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Some immune defenses of the brain may have their roots in the gut.

A new study in mice finds that immune cells are first trained in the gut to recognize and launch attacks on pathogens, and then migrate to the brain’s surface to protect it, researchers report online November 4 in Nature. These cells were also found in surgically removed parts of human brains.

Every minute, around 750 milliliters of blood flow through the brain, giving bacteria, viruses or other blood-borne pathogens an opportunity to infect the organ. For the most part, the invaders are kept out by three membrane layers, called the meninges, which wrap around the brain and spinal cord and act as a physical barrier. If a pathogen does manage to breach that barrier, the researchers say, the immune cells trained in the gut are ready to attack by producing a battalion of antibodies.

The most common route for a pathogen to end up in the bloodstream is from the gut. “So, it makes perfect sense for these [immune cells] to be educated, trained and selected to recognize things that are present in the gut,” says Menna Clatworthy, an immunologist at the University of Cambridge.

Clatworthy’s team found antibody-producing plasma cells in the leathery meninges, which lie between the brain and skull, in both mice and humans. These immune cells produced a class of antibodies called immunoglobulin A, or IgA.

These cells and antibodies are mainly found in the inner lining of the gut and lungs, so the scientists wondered if the cells on the brain had any link to the gut. It turned out that there was: Germ-free mice, which had no microbes in their guts, didn’t have any plasma cells in their meninges either. However, when bacteria from the poop of other mice and humans were transplanted into the mice’s intestines, their gut microbiomes were restored, and the plasma cells then appeared in the meninges.

“This was a powerful demonstration of how important the gut could be at determining what is found in the meninges,” Clatworthy says.

Researchers captured microscope images of an attack in the meninges of mice that was led by plasma cells that had likely been trained in the guts. When the team implanted a pathogenic fungus, commonly found in the intestine, into the mice’s bloodstream, the fungus attempted to enter the brain through the walls of blood vessels in the meninges. However, plasma cells in the membranes formed a mesh made of IgA antibodies around the pathogen, blocking its entry. The plasma cells are found along the blood vessels, Clatworthy says, where they can quickly launch an attack on pathogens.

“To my knowledge, this is the first time anyone has shown the presence of plasma cells in the meninges. The study has rewritten the paradigm of what we know about these plasma cells and how they play a critical role in keeping our brain healthy,” says Matthew Hepworth, an immunologist at the University of Manchester in England who was not involved with the study. More research is needed to classify how many of the plasma cells in the meninges come from the gut, he says.

The finding adds to growing evidence that gut microbes can play a role in brain diseases. A previous study, for instance, suggested that in mice, boosting a specific gut bacterium could help fight amyotrophic lateral sclerosis, or ALS, a fatal neurological disease that results in paralysis (SN: 7/22/19). And while the new study found the plasma cells in the brains of healthy mice, previous research has found other gut-trained cells in the brains of mice with multiple sclerosis, an autoimmune disease of the brain and the spinal cord.

For now, the researchers want to understand what cues plasma cells follow in the guts to know it is time for them to embark on a journey to the brain.

It’s official: 2020 now has the most named storms ever recorded in the Atlantic in a single year.

On November 9, a tropical disturbance brewing in the northeastern Atlantic Ocean gained enough strength to become a subtropical storm. With that, Theta became the year’s 29th named storm, topping the 28 that formed in 2005.

With maximum sustained winds near 110 kilometers per hour as of November 10, Theta is expected to churn over the open ocean for several days. It’s too early to predict Theta’s ultimate strength and trajectory, but forecasters with the National Oceanic and Atmospheric Administration say they expect the storm to weaken later in the week.

If so, like most of the storms this year, Theta likely won’t become a major hurricane. That track record might be the most surprising thing about this season — there’s been a record-breaking number of storms, but overall they’ve been relatively weak. Only five — Laura, Teddy, Delta, Epsilon and Eta — have become major hurricanes with winds topping 178 kilometers per hour, although only Laura and Eta made landfall near the peak of their strength as Category 4 storms.

Even so, the 2020 hurricane season started fast, with the first nine storms arriving earlier than ever before (SN: 9/7/20). And the season has turned out to be the most active since naming began in 1953, thanks to warmer-than-usual water in the Atlantic and the arrival of La Niña, a regularly-occurring period of cooling in the Pacific, which affects winds in the Atlantic and helps hurricanes form (SN: 9/21/19). If a swirling storm reaches wind speeds of 63 kilometers per hour, it gets a name from a list of 21 predetermined names. When that list runs out, the storm gets a Greek letter.

While the wind patterns and warm Atlantic water temperatures set the stage for the string of storms, it’s unclear if climate change is playing a role in the number of storms. As the climate warms, though, you would expect to see more of the destructive, high-category storms, says Kerry Emanuel, an atmospheric scientist at MIT. “And this year is not a poster child for that.” So far, no storm in 2020 has been stronger than a Category 4. The 2005 season had multiple Category 5 storms, including Hurricane Katrina (SN: 12/20/05).

There’s a lot amount of energy in the ocean and atmosphere this year, including the unusually warm water, says Emanuel. “The fuel supply could make a much stronger storm than we’ve seen,” says Emanuel, “so the question is: What prevents a lot of storms from living up to their potential?”
A major factor is wind shear, a change in the speed or direction of wind at different altitudes. Wind shear “doesn’t seem to have stopped a lot of storms from forming this year,” Emanuel says, “but it inhibits them from getting too intense.” Hurricanes can also create their own wind shear, so when multiple hurricanes form in close proximity, they can weaken each other, Emanuel says. And at times this year, several storms did occupy the Atlantic simultaneously — on September 14, five storms swirled at once.

It’s not clear if seeing hurricane season run into the Greek alphabet is a “new normal,” says Emanuel. The historical record, especially before the 1950s is spotty, he says, so it’s hard to put this year’s record-setting season into context. It’s possible that there were just as many storms before naming began in the ‘50s, but that only the big, destructive ones were recorded or noticed. Now, of course, forecasters have the technology to detect all of them, “so I wouldn’t get too bent out of shape about this season,” Emanuel says.

Some experts are hesitant to even use the term “new normal.”

“People talk about the ‘new normal,’ and I don’t think that is a good phrase,” says James Done, an atmospheric scientist at the National Center for Atmospheric Research in Boulder, Colo. “It implies some new stable state. We’re certainly not in a stable state — things are always changing.”

When some bacteria manage to escape being killed by a virus, the microbes end up hamstringing themselves. And that could be useful in the fight to treat infections.

The bacterium Shigella flexneri — one cause of the infectious disease shigellosis — can spread within cells that line the gut by propelling itself through the cells’ barriers. That causes tissue damage that can lead to symptoms like bloody diarrhea. But when S. flexneri in lab dishes evolved to elude a type of bacteria-killing virus, the bacteria couldn’t spread cell to cell anymore, making it less virulent, researchers report November 17 in Applied and Environmental Microbiology.

The research is a hopeful sign for what’s known as phage therapy (SN: 11/20/02). With antibiotic-resistant microbes on the rise, some researchers see viruses that infect and kill only bacteria, known as bacteriophages or just phages, as a potential option to treat antibiotic-resistant infections (SN: 11/13/19). With phage therapy, infected people are given doses of a particular phage, which kill off the problematic bacteria. The problem, though, is that over time those bacteria can evolve to be resistant against the phage, too.

“We’re kind of expecting phage therapy to fail, in a sense,” says Paul Turner, an evolutionary biologist and virologist at Yale University. “Bacteria are very good at evolving resistance to phages.”
But that doesn’t mean the bacteria emerge unscathed. Some phages attack and enter bacteria by latching onto bacterial proteins crucial for a microbe’s function. If phage therapy treatments relied on such a virus, that could push the bacteria to evolve in such a way that not only helps them escape the virus but also impairs their abilities and makes them less deadly. People infected with these altered bacteria might have less severe symptoms or may not show symptoms at all.

Previous studies with the bacteria Pseudomonas aeruginosa, for instance, have found that phage and bacteria can engage in evolutionary battles that drive the bacteria to be more sensitive to antibiotics. The new study hints that researchers could leverage the arms race between S. flexneri and the newly identified phage, which was dubbed A1-1 after being found in Mexican wastewater, to treat shigellosis.

S. flexneri in contaminated water is a huge problem in parts of the world where clean water isn’t always available, such as sub-Saharan Africa and southern Asia, says Kaitlyn Kortright, a microbiologist also at Yale University. Every year, approximately 1.3 million people die from shigellosis, which is caused by four Shigella species. More than half of those deaths are in children younger than 5 years old. What’s more, antibiotics to treat shigellosis can be expensive and hard to access in those places. And S. flexneri is becoming resistant to many antibiotics. Phage therapy could be a cheaper, more accessible option to treat the infection.

The blow to S. flexneri’s cellular spread comes because to enter cells, A1-1 targets a protein called OmpA, which is crucial for the bacteria to rupture host cell membranes. The researchers found two types of mutations that made S. flexneri resistant to A1-1. Some bacteria had mutations in the gene that produces OmpA, damaging the protein’s ability to help the microbes spread from cell to cell. Others had changes to a structural component of bacterial cells called lipopolysaccharide.

The mutations in lipopolysaccharide were surprising, Kortright says, because the relationship between that structural component and OmpA isn’t fully worked out. One possibility is that those mutations distort OmpA’s structure in a way that the phage no longer recognizes it and can’t enter bacterial cells.

One lingering question is whether S. flexneri evolves in the same way outside a lab dish, says Saima Aslam, an infectious diseases physician at the University of California, San Diego who was not involved in the work. Still, the findings show that it’s “not always a bad thing” when bacteria become phage-resistant, she says.

The twilight time between fully awake and sound asleep may be packed with creative potential.

People who recently drifted off into a light sleep later had problem-solving power, scientists report December 8 in Science Advances. The results help demystify the fleeting early moments of sleep and may even point out ways to boost creativity.

Prolific inventor and catnapper Thomas Edison was rumored to chase those twilight moments. He was said to fall asleep in a chair holding two steel ball bearings over metal pans. As he drifted off, the balls would fall. The ensuing clatter would wake him, and he could rescue his inventive ideas before they were lost to the depths of sleep.

Delphine Oudiette, a cognitive neuroscientist at the Paris Brain Institute, and colleagues took inspiration from Edison’s method of cultivating creativity. She and her colleagues brought 103 healthy people to their lab to solve a tricky number problem. The volunteers were asked to convert a string of numbers into a shorter sequence, following two simple rules. What the volunteers weren’t told was that there was an easy trick: The second number in the sequence would always be the correct final number, too. Once discovered, this cheat code dramatically cut the solving time.
After doing 60 of these trials on a computer, the volunteers earned a 20-minute break in a quiet, dark room. Reclined and holding an equivalent of Edison’s “alarm clock” (a light drinking bottle in one dangling hand), participants were asked to close their eyes and rest or sleep if they desired. All the while, electrodes monitored their brain waves.

About half of the participants stayed awake. Twenty-four fell asleep and stayed in the shallow, fleeting stage of sleep called N1. Fourteen people progressed to a deeper stage of sleep called N2.

After their rest, participants returned to their number problem. The researchers saw a stark difference between the groups: People who had fallen into a shallow, early sleep were 2.7 times as likely to spot the hidden trick as people who didn’t fall asleep, and 5.8 times as likely to spot it as people who had reached the deeper N2 stage.

Such drastic differences in these types of experiments are rare, Oudiette says. “We were quite astonished by the extent of the results.” The researchers also identified a “creative cocktail of brain waves,” as Oudiette puts it, that seemed to accompany this twilight stage — a mixture of alpha brain waves that usually mark relaxation mingled with the delta waves of deeper sleep.

The study doesn’t show that the time spent in N1 actually triggered the later realization, cautions John Kounios, a cognitive neuroscientist at Drexel University in Philadelphia who cowrote the 2015 book The Eureka Factor: Aha Moments, Creative Insight, and the Brain. “It could have been possible that grappling with the problem and initiating an incubation process caused both N1 and the subsequent insight,” he says, making N1 a “by-product of the processes that caused insight rather than the cause.”

More work is needed to untangle the connection between N1 and creativity, Oudiette says. But the results raise a tantalizing possibility, one that harkens to Edison’s self-optimizations: People might be able to learn to reach that twilight stage of sleep, or to produce the cocktail of brain waves associated with creativity on demand.

It seems Edison was onto something about the creative powers of nodding off. But don’t put too much stock in his habits. He is also said to have considered sleep “a criminal waste of time.”

2021 was the year the COVID-19 vaccines had to prove their mettle. We started the year full of hope: With vaccines in hand in record-breaking time and their rollout ramping up, we’d get shots in arms, curb this pandemic and get life back to normal. That was too optimistic.

Roughly 200 million people in the United States — and billions globally — have now been fully vaccinated. Three vaccines — one from Pfizer and its partner BioNTech, and the other two from Moderna and Johnson & Johnson — are available in the United States. Pfizer’s is even available for children as young as 5. About two dozen other vaccines have also been deployed in other parts of the world. In some higher-income countries, the United States included, people have already queued up for booster shots.

But 2021 has also been the year of learning the limits of the vaccines’ superpowers. With the vaccines pitted against aggressive coronavirus variants, inequitable distribution, some people’s hesitancy and the natural course of waning effectiveness, there’s still a lot of work to do to bring this pandemic to an end. As if to hammer home that point, the detection of the omicron variant in late November brought new uncertainty to the pandemic’s trajectory. Here are some of the top lessons we’ve learned in the first year of the COVID-19 vaccine. — Macon Morehouse
The shots work, even against emerging variants
Many COVID-19 vaccines proved effective over the last year, particularly at preventing severe disease and death (SN: 10/9/21 & 10/23/21, p. 4). That’s true even with the emergence of more transmissible coronavirus variants.

In January, in the midst of a bleak winter surge that saw average daily cases in the United States peaking at nearly 250,000, the vaccination rollout here began in earnest. Soon after, case numbers began a steep decline.

Over the summer, though, more reports of coronavirus infections in vaccinated people began to pop up. Protection against infection becomes less robust in the months following vaccination in people who received Pfizer’s or Moderna’s mRNA vaccines, multiple studies have shown (SN Online: 9/21/21). Yet the shots’ original target — preventing hospitalization — has held steady, with an efficacy of about 80 percent to 95 percent.
A single dose of Johnson & Johnson’s vaccine is less effective at preventing symptoms or keeping people out of the hospital than the mRNA jabs. The company claims there’s not yet evidence that the protection wanes. But even if that protection is not waning, some real-world data hint that the shot may not be as effective as clinical trials suggested (SN Online: 10/19/21).

Evidence of waning or lower protection ultimately pushed the United States and some other countries to green-light COVID-19 booster shots for adults (SN: 12/4/21, p. 6).

Much of the worry over waning immunity came amid the spread of highly contagious variants, including alpha, first identified in the United Kingdom in September 2020, and delta, first detected in India in October 2020 (SN Online: 7/30/21). Today, delta is the predominant variant globally.

The good news is that vaccinated people aren’t unarmed against these mutated foes. The immune system launches a multipronged attack against invaders, so the response can handle small molecular tweaks to viruses, says Nina Luning Prak, an immunologist at the University of Pennsylvania. Dealing with variants “is what the immune system does.”
Vaccine-prompted antibodies still attack alpha and delta, though slightly less well than they tackle the original virus that emerged in Wuhan, China, two years ago. Antibodies also still recognize more immune-evasive variants such as beta, first identified in South Africa in May 2020, and gamma, identified in Brazil in November 2020. Although protection against infection dips against many of these variants, vaccinated people remain much less likely to be hospitalized compared with unvaccinated people.
Experts will continue to track how well the vaccines are doing, especially as new variants, like omicron, emerge. In late November, the World Health Organization designated the omicron variant as the latest variant of concern after researchers in South Africa and Botswana warned that it carries several worrisome mutations. Preliminary studies suggest that, so far, omicron is spreading fast in places including South Africa and the United Kingdom, and can reinfect people who have already recovered from an infection. The variant might be at least as transmissible as delta, though that’s still far from certain, according to a December 9 report from researchers with Public Health England, a U.K. health agency. How omicron may affect vaccine effectiveness is also unclear. Pfizer’s two-dose shot, for instance, may be about 30 percent effective at preventing symptoms from omicron infections while a booster could bring effectiveness back up to more than 70 percent, according to estimates from Public Health England. But those estimates are based on low case numbers and could change as omicron spreads.

“This is the first time in history that we’re basically monitoring virus mutations in real time,” says Müge Çevik, an infectious diseases physician and virologist at the University of St. Andrews in Scotland. “This is what the viruses do. It’s just that we’re seeing it because we’re looking for it.”

But it’s unlikely that any new variant will take us back to square one, Çevik says. Because of the immune system’s varied defenses, it will be difficult for a coronavirus variant to become completely resistant to vaccine-induced protection. The vaccines are giving our immune systems the tools to fight back. — Erin Garcia de Jesús

The shots are safe, with few serious side effects
With billions of doses distributed around the world, the shots have proved not only effective, but also remarkably safe, with few serious side effects.

“We have so much safety data on these vaccines,” says Kawsar Talaat, an infectious diseases physician at the Johns Hopkins Bloomberg School of Public Health. “I don’t know of any vaccines that have been scrutinized to the same extent.”

Commonly reported side effects include pain, redness or swelling at the spot of the shot, muscle aches, fatigue, fever, chills or a headache. These symptoms usually last only a day or two.
More rare and serious side effects have been noted. But none are unique to these shots; other vaccines — plus infectious diseases, including COVID-19 — also cause these complications.

One example is inflammation of the heart muscle, known as myocarditis, or of the sac around the heart, pericarditis. Current estimates are a bit squishy since existing studies have different populations and other variables (SN Online: 10/19/21). Two large studies in Israel estimated that the risk of myocarditis after an mRNA vaccine is about 4 of every 100,000 males and 0.23 to 0.46 of every 100,000 females, researchers reported in October in the New England Journal of Medicine. Yet members of Kaiser Permanente Southern California who had gotten mRNA vaccines developed myocarditis at a much lower rate: 5.8 cases for every 1 million second doses given, researchers reported, also in October, in JAMA Internal Medicine.

What all the studies have in common is that young males in their teens and 20s are at highest risk of developing the side effect, and that risk is highest after the second vaccine dose (SN Online: 6/23/21). But it’s still fairly rare, topping out at about 15 cases for every 100,000 vaccinated males ages 16 to 19, according to the larger of the two Israeli studies. Males in that age group are also at the highest risk of getting myocarditis and pericarditis from any cause, including from COVID-19.
Components of the mRNA vaccines may also cause allergic reactions, including potentially life-threatening anaphylaxis. The U.S. Centers for Disease Control and Prevention calculated that anaphylaxis happens at a rate of about 0.025 to 0.047 cases for every 10,000 vaccine doses given.

But a study of almost 65,000 health care system employees in Massachusetts suggests the rate may be as high as 2.47 per 10,000 vaccinations, researchers reported in March in JAMA. Still, that rate is low, and people with previous histories of anaphylaxis have gotten the shots without problem. Even people who developed anaphylaxis after a first shot were able to get fully vaccinated if the second dose was broken down into smaller doses (SN Online: 6/1/21).

The only side effect of the COVID-19 vaccines not seen with other vaccines is a rare combination of blood clots accompanied by low numbers of blood-clotting platelets. Called thrombosis with thrombocytopenia syndrome, or TTS, it’s most common among women younger than 50 who got the Johnson & Johnson vaccine or a similar vaccine made by AstraZeneca that’s used around the world (SN Online: 4/23/21).
About 5 to 6 TTS cases were reported for every 1 million doses of the J&J vaccine, the company reported to the U.S. Food and Drug Administration. The clots may result from antibodies triggering a person’s platelets to form clots (SN Online: 4/16/21). Such antibodies also cause blood clots in COVID-19 patients, and the risk of developing strokes or clots from the disease is much higher than with the vaccine, Talaat says. In one study, 42.8 of every 1 million COVID-19 patients developed one type of blood clot in the brain, and 392.3 per 1 million developed a type of abdominal blood clot, researchers reported in EClinicalMedicine in September.

“Your chances of getting any of these side effects, except for the sore arm, from an illness with COVID are much higher” than from the vaccines, Talaat says. — Tina Hesman Saey

Getting everyone vaccinated is … complicated
The quest to vaccinate as many people as quickly as possible this year faced two main challenges: getting the vaccine to people and convincing them to take it. Strategies employed so far — incentives, mandates and making shots accessible — have had varying levels of success.

“It’s an incredibly ambitious goal to try to get the large majority of the country and the globe vaccinated in a very short time period with a brand-new vaccine,” says psychologist Gretchen Chapman of Carnegie Mellon University in Pittsburgh, who researches vaccine acceptance. Usually “it takes a number of years before you get that kind of coverage.”
Globally, that’s sure to be the case due to a lack of access to vaccines, particularly in middle- and lower-income countries. The World Health Organization set a goal to have 40 percent of people in all countries vaccinated by year’s end. But dozens of countries, mostly in Africa and parts of Asia, are likely to fall far short of that goal.

In contrast, the United States and other wealthy countries got their hands on more than enough doses. Here, the push to vaccinate started out with a scramble to reserve scarce appointments for a free shot at limited vaccination sites. But by late spring, eligible people could pop into their pharmacy or grocery store. Some workplaces offered vaccines on-site. For underserved communities that may have a harder time accessing such vaccines, more targeted approaches where shots are delivered by trusted sources at community events proved they could boost vaccination numbers (SN Online: 6/18/21).

Simply making the shot easy to get has driven much of the progress made so far, Chapman says. But getting people who are less enthusiastic has proved more challenging. Many governments and companies have tried to prod people, initially with incentives, later with mandates.
Free doughnuts, direct cash payments and entry into million-dollar lottery jackpots were among the many perks rolled out. Before the pandemic, such incentives had been shown to prompt some people to get vaccines, says Harsha Thirumurthy, a behavioral economist at the University of Pennsylvania. This time, those incentives made little difference nationwide, Thirumurthy and his colleagues reported in September in a preliminary study posted to SSRN, a social sciences preprint website. “It’s possible they moved the needle 1 or 2 percentage points, but we’ve ruled out that they had a large effect,” he says. Some studies of incentives offered by individual states have found a marginal benefit.

“People who are worried about side effects or safety are going to be more difficult to reach,” says Melanie Kornides, an epidemiologist at the University of Pennsylvania. And with vaccination status tangled up in personal identity, “you’re just not going to influence lots of people with a mass communication campaign right now; it’s really about individual conversations,” she says, preferably with someone trusted.
“Or,” she adds, “they’re going to respond to mandates.” Historically, sticks such as being fired from a job or barred from school are the most effective way of boosting vaccination rates, Kornides says. For example, hospitals that require flu shots for workers tend to have higher vaccination rates than those that don’t. For decades, mandates in schools have helped push vaccination rates up for diseases like measles and chickenpox, she says.

As COVID-19 mandates went into effect in the fall, news headlines often focused on protests and refusals. Yet early anecdotal evidence suggests some mandates have helped. For instance, after New York City public schools announced a vaccine requirement in late August for its roughly 150,000 employees, nearly 96 percent had received at least one shot by early November. Still, about 8,000 employees opted not to get vaccinated and were placed on unpaid leave, the New York Times reported.

Many people remain vehemently opposed to the vaccines, in part because of rampant misinformation that can spread quickly online. Whether more mandates, from the government or private companies, and targeted outreach will convince them remains to be seen. — Jonathan Lambert

Vaccines can’t single-handedly end the pandemic
One year in, it’s clear that vaccination is one of the best tools we have to control COVID-19. But it’s also clear vaccines alone can’t end the pandemic.

While the jabs do a pretty good job preventing infections, that protection wanes over time (SN Online: 3/30/21). Still, the vaccines have “worked spectacularly well” at protecting most people from severe disease, says Luning Prak, the University of Pennsylvania immunologist. And as more people around the world get vaccinated, fewer people will die, even if they do fall ill with COVID-19.

“We have to make a distinction between the superficial infections you can get — [like a] runny nose — versus the lower respiratory tract stuff that can kill you,” such as inflammation in the lungs that causes low oxygen levels, Luning Prak says. Preventing severe disease is the fundamental target that most vaccines, including the flu shot, hit, she notes. Stopping infection entirely “was never a realistic goal.”
Because vaccines aren’t an impenetrable barrier against the virus, we’ll still need to rely on other tactics to help control spread amid the pandemic. “Vaccines are not the sole tool in our toolbox,” says Saad Omer, an epidemiologist at Yale University. “They should be used with other things,” such as masks to help block exposure and COVID-19 tests to help people know when they should stay home.

For now, it’s crucial to have such layered protection, Omer says. “But in the long run, I think vaccines provide a way to get back to at least a new normal.” With vaccines, people can gather at school, concerts or weddings with less fear of a large outbreak.

Eventually the pandemic will end, though when is still anyone’s guess. But the end certainly won’t mean that COVID-19 has disappeared.

Many experts agree that the coronavirus will most likely remain with us for the foreseeable future, sparking outbreaks in places where there are pockets of susceptible people. Susceptibility can come in many forms: Young children who have never encountered the virus before and can’t yet get vaccinated, people who choose not to get the vaccine and people whose immunity has waned after an infection or vaccination. Or the virus may evolve in ways that help it evade the immune system.

The pandemic’s end may still feel out of reach, with the high hopes from the beginning of 2021 a distant memory. Still, hints of normalcy have returned: Kids are back in school, restaurants and stores are open and people are traveling more.

Vaccines have proved to be an invaluable tool to reduce the death and destruction that the coronavirus can leave in its wake. — Erin Garcia de Jesús

Brains are like sponges, slurping up new information. But sponges may also be a little bit like brains.

Sponges, which are humans’ very distant evolutionary relatives, don’t have nervous systems. But a detailed analysis of sponge cells turns up what might just be an echo of our own brains: cells called neuroids that crawl around the animal’s digestive chambers and send out messages, researchers report in the Nov. 5 Science.

The finding not only gives clues about the early evolution of more complicated nervous systems, but also raises many questions, says evolutionary biologist Thibaut Brunet of the Pasteur Institute in Paris, who wasn’t involved in the study. “This is just the beginning,” he says. “There’s a lot more to explore.”

The cells were lurking in Spongilla lacustris, a freshwater sponge that grows in lakes in the Northern Hemisphere. “We jokingly call it the Godzilla of sponges” because of the rhyme with Spongilla, say Jacob Musser, an evolutionary biologist in Detlev Arendt’s group at the European Molecular Biology Laboratory in Heidelberg, Germany.

Simple as they are, these sponges have a surprising amount of complexity, says Musser, who helped pry the sponges off a metal ferry dock using paint scrapers. “They’re such fascinating creatures.”
With sponges procured, Arendt, Musser and colleagues looked for genes active in individual sponge cells, ultimately arriving at a list of 18 distinct kinds of cells, some known and some unknown. Some of these cells used genes that are essential to more evolutionarily sophisticated nerve cells in other organisms for sending or receiving messages in the form of small blobs of cellular material called vesicles.

One such cell, called a neuroid, caught the scientists’ attention. After seeing that this cell was using those genes involved in nerve cell signaling, the researchers took a closer look. A view through a confocal microscope turned up an unexpected locale for the cells, Musser says. “We realized, ‘My God, they’re in the digestive chambers.’”

Large, circular digestive structures called choanocyte chambers help move water and nutrients through sponges’ canals, in part by the beating of hairlike cilia appendages (SN: 3/9/15). Neuroids were hovering around some of these cilia, the researchers found, and some of the cilia near neuroids were bent at angles that suggested that they were no longer moving.
The team suspects that these neuroids were sending signals to the cells charged with keeping the sponge fed, perhaps using vesicles to stop the movement of usually undulating cilia. If so, that would be a sophisticated level of control for an animal without a nervous system.

The finding suggests that sponges are using bits and bobs of communications systems that ultimately came together to work as brains of other animals. Understanding the details might provide clues to how nervous systems evolved. “What did animals have, before they had a nervous system?” Musser asks. “There aren’t many organisms that can tell us that. Sponges are one of them.”

As the chill of autumn encroaches on Siberia’s grasslands, Richard’s pipits usually begin their southward trek to warmer latitudes. But a growing number of the slender, larklike songbirds seem to be heading west instead, possibly establishing a new migratory route for the species.

This would be the first new route known to emerge on an east-west axis in a long-distance migratory bird, researchers report October 22 in Current Biology. The finding could have implications for how scientists understand the evolution of bird migration routes over time and how the animals adapt to a shifting climate.

Richard’s pipits (Anthus richardi) typically breed in Siberia during the summer and travel south for the winter to southern Asia. Occasionally, “vagrant” birds get lost and show up far from this range, including in Europe. But as a Ph.D. student at the Université Grenoble Alpes in France, evolutionary biologist Paul Dufour noticed, along with colleagues, that described sightings and photo records of the pipits wintering in southern France had increased from a handful of birds annually in the 1980s and 1990s to many dozens in recent years.

So, Dufour, now at the University of Gothenburg in Sweden, and his team started monitoring the pipits in France and Spain to see where the birds were coming from, and if the birds were visiting Europe on purpose or just getting lost.

The researchers captured seven pipits in France during the winter of 2019–2020, tagging them with a sensor that estimates the birds’ geographic positions based on light levels and length of day. The team then released the birds. The next winter, the team successfully recaptured three of them. Those sensors showed that the birds had all flown back to the same part of southwestern Siberia for the summer before returning to France.

The researchers also examined images in citizen-science databases of 331 Richard’s pipits that were photographed in Europe and North Africa, categorizing the birds by apparent age. Among songbirds, Dufour says, vagrants are always young birds. Songbirds tend to follow a route based on instincts written into their DNA, replicating the trip their ancestors took. But storms or mutations that create faulty wayfinding abilities can send young songbirds off target.
Wherever it arrives, the songbird’s first migration creates a mental map for every migration after, so any adult birds in Europe have made the trip more than once. Since more than half of the birds in southern Europe and nearby northwestern Africa documented in the winter were adults, Dufour and his colleagues think that many of these pipits are seasonal migrants.

Contemporary shifts in migration routes are more common in species that travel via the cues of a traveling group, like geese or cranes. Songbirds usually migrate alone, following their instinctual route when young, Dufour says, so changes to migration patterns are rarer.

What’s more, east-west migration is unusual in birds. Most species that travel this way are ones that migrate short distances within the tropics, says Jessie Williamson, an ornithologist at the University of New Mexico in Albuquerque who was not involved with the research. “It’s exciting that an understudied migratory behavior like east-west migration is in the spotlight,” she says.

If the pipits’ European trek is in fact now an established route, it’s possible that the detour was facilitated by climate change, which may also be meddling with birds’ migrations in other ways (SN: 12/17/19). Dufour and his team used computer models that estimate climate suitability for the pipits in Europe based on variables like temperature and precipitation. The researchers compared two periods — 1961 to 1990 and 1990 to 2018 — and found that warmer temperatures in the latter period have made most parts of southern Europe a better wintering location for the birds than they were before.
The selection of European wintering grounds may also involve the deterioration of ancestral, southern Asian sites, but the researchers haven’t investigated that yet. Climate change could be affecting that too, Dufour says. But “we suspect that habitat modification in Southeast Asia — increasing urbanization, less open areas — may also be part of the equation.”

Ginny Chan, an ecologist at the Swiss Ornithological Institute in Sempach who was not involved with the research, says that the types of environmental changes that could be hurting bird populations “are happening very quickly in the traditional wintering range [for Richard’s pipits] in South and East Asia.” In India, the Richard’s pipit population has declined by more than 90 percent over the last couple of decades, Chan says.

Other Siberian bird species that typically migrate south but have recently shown up in Europe in growing numbers, like the yellow-browed warbler and Siberian chiffchaff, may also be making their own westward routes, Dufour suspects.

If other Siberian songbird species are also establishing new western migration routes, this could mean that migratory songbirds are more flexible travelers than scientists previously thought, Dufour says.

That could have hopeful implications for some birds as species worldwide deal with a changing climate. But the new research, he adds, shouldn’t overshadow other studies of migratory birds — like barnacle geese and the European pied flycatcher — which show that some of these species are not as able to cope with climate change.

In a remote corner of Brazil’s Amazon rainforest, researchers have spent decades catching and measuring birds in a large swath of forest unmarred by roads or deforestation. An exemplar of the Amazon’s dazzling diversity, the experimental plot was to act as a baseline that would reveal how habitat fragmentation, from logging or roads, can hollow out rainforests’ wild menagerie.

But in this pristine pocket of wilderness, a more subtle shift is happening: The birds are shrinking.

Over 40 years, dozens of Amazonian bird species have declined in mass. Many species have lost nearly 2 percent of their average body weight each decade, researchers report November 12 in Science Advances. What’s more, some species have grown longer wings. The changes coincide with a hotter, more variable climate, which could put a premium on leaner, more efficient bodies that help birds stay cool, the researchers say.

“Climate change isn’t something of the future. It’s happening now and has been happening and has effects we haven’t thought of,” says Ben Winger, an ornithologist at the University of Michigan in Ann Arbor who wasn’t involved in the research but has documented similar shrinkage in migratory birds. Seeing the same patterns in so many bird species across widely different contexts “speaks to a more universal phenomenon,” he says.

Biologists have long linked body size and temperature. In colder climates, it pays to be big because having a smaller surface area relative to one’s volume reduces heat loss through the skin and keeps the body warmer. As the climate warms, “you’d expect shrinking body sizes to help organisms off-load heat better,” says Vitek Jirinec, an ecologist at the Integral Ecology Research Center in Blue Lake, Calif.

Many species of North American migratory birds are getting smaller, Winger and colleagues reported in 2020 in Ecology Letters. Climate change is the likely culprit, Winger says, but since migrators experience a wide range of conditions while globe-trotting, other factors such as degraded habitats that birds may encounter can’t be ruled out.

To see if birds that stay put have also been shrinking, Jirinec and colleagues analyzed data on nonmigratory birds collected from 1979 to 2019 in an intact region of the Amazon that spans 43 kilometers. The dataset includes measurements such as mass and wing length for over 11,000 individual birds of 77 species. The researchers also examined climate data for the region.
All species declined in mass over this period, the researchers found, including birds as different as the Rufous-capped antthrush (Formicarius colma), which snatches insects off the forest floor, and the Amazonian motmot (Momotus momota), which scarfs down fruit up in trees. Species lost from about 0.1 percent to nearly 2 percent of their average body weight each decade. The motmot, for example, shrunk from 133 grams to about 127 grams over the study period.

These changes coincided with an overall increase in the average temperature of 1 degree Celsius in the wet season and 1.65 degrees C in the dry season. Temperature and precipitation also became more variable over the time period, and these short-term fluctuations, such as an especially hot or dry season, better explained the size trends than the steady increase in temperature.

“The dry season is really stressful for birds,” Jirinec says. Birds’ mass decreased the most in the year or two after especially hot and dry spells, which tracks with the idea that birds are getting smaller to deal with heat stress.

Other factors, like decreased food availability, could also lead to smaller sizes. But since birds with widely different diets all declined in mass, a more pervasive force like climate change is the likely cause, Jirinec says.

Wing length also grew for 61 species, with a maximum increase of about 1 percent per decade. Jirinec thinks that longer wings make for more efficient, and thus cooler, fliers. For instance, a fighter jet, with its heavy body and compact wings, takes enormous power to maneuver. A light and long-winged glider, by contrast, can cruise along much more efficiently.

“Longer wings may be helping [birds] fly more efficiently and produce less metabolic heat,” which can be beneficial in hotter conditions, he says. “But that’s just a hypothesis.” This body change was most pronounced in birds that spend their time higher up in the canopy, where conditions are hotter and drier than the forest floor.

Whether these changes in shape and size represent an evolutionary adaptation to climate change, or simply a physiological response to warmer temperatures, remains unclear (SN: 5/8/20). Whichever is the case, Jirinec suggests that the change shows the pernicious power of human activity (SN: 10/26/21).

“The Amazon rainforest is mysterious, remote and teeming with biodiversity,” he says. “This study suggests that even in places like this, far removed from civilization, you can see signatures of climate change.”

Regenerating body parts is never easy. For instance, some lizards can grow back their tails, but these new appendages are pale imitations of the original. Now, genetically modified stem cells are helping geckos grow back better tails.

Tweaking and implanting embryonic stem cells on the tail stumps of mourning geckos (Lepidodactylus lugubris) allowed the reptiles to grow tails that are more like the original than ever before, researchers report October 14 in Nature Communications. These findings are a stepping-stone to developing regenerative therapies in humans that may one day treat hard-to-heal wounds.

A gecko’s tail is an extension of its spine — with the vertebrae to prove it. Regenerated tails, however, are simpler affairs. “It’s just a bunch of concentric tubes of fat, muscle and skin,” says Thomas Lozito, a biologist at the University of Southern California in Los Angeles.

That’s because stem cells in adult geckos produce a molecular signal that encourages the formation of cartilage in new tails, but not bone or nervous tissues (SN: 8/17/18). Lozito and his colleagues used embryonic stem cells, which can develop into a wider range of tissues than adult stem cells, modified them to ignore this signal and then implanted them on the tail stumps of geckos that had their tails surgically removed. The tails that grew from these modified stem cells had bonelike grooves in the cartilage and generated new neural tissue at the top of the tail.

These modified tails still lack a spinal cord, making them a far cry from the original. “We fixed one problem, but there are still many imperfections,” Lozito says. “We’re still on the hunt for the perfect tail.”

Mystery mummies from Central Asia have a surprising ancestry. These people, who displayed facial characteristics suggesting a European heritage, belonged to a local population with ancient Asian roots, a new study finds. Until now, researchers had pegged the mummified Bronze Age bunch as newcomers and debated about where in West Asia they originally came from.

Desert heat naturally mummified hundreds of bodies buried in western China’s Tarim Basin from roughly 4,000 to 1,800 years ago. Preserved remains of these people have been excavated since the 1990s (SN: 2/25/95). Those interred around 4,000 years ago belonged to the Xiaohe culture, a population that mixed animal herding with plant cultivation. Their boat-shaped coffins were unlike any others in the region. And preserved cheese, wheat, millet and clothes made from western Eurasian wool found in Xiaohe graves pointed to distant contacts or origins.

Archaeogeneticist Yinqiu Cui of Jilin University in Changchun, China, and an international team analyzed DNA from 13 Tarim Basin mummies from roughly 4,100 to 3,700 years ago and five other human mummies from the nearby Dzungarian Basin from around 5,000 to 4,800 years ago.
Tarim people displayed Asian ancestry mainly traceable to hunter-gatherers who inhabited much of northern Eurasia more than 9,000 years ago. That finding suggests that the mummies belonged to a population that did not mate with outsiders for many millennia, the researchers report October 27 in Nature. No DNA links were found to western Eurasian herders from the Afanasievo culture (SN: 11/15/17), who some researchers have regarded as precursors of Xiaohe people.

A predominantly Afanasievo ancestry did appear in the Dzungarian individuals. Milk proteins found in dental tartar from seven Tarim mummies indicated that those people regularly consumed dairy products, a practice possibly learned from Afanasievo descendants in the Dzungarian Basin, the researchers say.